Oxide thin film, methods of manufacturing oxide thin film and electronic devices including oxide thin film

ABSTRACT

Oxide thin film, electronic devices including the oxide thin film and methods of manufacturing the oxide thin film, the methods including (A) applying an oxide precursor solution comprising at least one of zinc (Zn), indium (In) and tin (Sn) on a substrate, (B) heat-treating the oxide precursor solution to form an oxide layer, and (C) repeating the steps (A) and (B) to form a plurality of the oxide layers.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 to Korean PatentApplication No. 10-2010-0027347 filed in the Korean IntellectualProperty Office (KIPO) on Mar. 26, 2010, the entire contents of which isincorporated herein by reference.

BACKGROUND

1. Field

Example embodiments relate to an oxide thin film, methods ofmanufacturing the oxide thin film and electronic devices including theoxide thin film.

2. Description of the Related Art

Electronic devices such as resistors, capacitors, diodes and thin filmtransistors are used in various fields. Thin film transistors (TFT) maybe used as switching and driving devices in a flat panel display such asa liquid crystal display (LCD), an organic light emitting diode display(OLED display) or an electrophoretic display (EPD).

Electronic devices such as thin film transistors may include asemiconductor thin film deposited using semiconductor processing (e.g.,chemical vapor deposition (CVD)). According to the deposition method,the manufacturing cost of semiconductor devices may be high and themanufacturing processes thereof complicated.

In order to simplify semiconductor thin film deposition processes, asemiconductor thin film may be formed by a solution process using aprecursor solution. However, a semiconductor thin film formed by asolution process results in a semiconductor device with poor ordeteriorated semiconductor characteristics and reduced reliability ascompared to a semiconductor thin film formed by other depositionmethods.

SUMMARY

Example embodiments may provide an oxide thin film with improvedreliability, methods of manufacturing the oxide thin film using simpleand reduced complexity processes and electronic devices including theoxide thin film.

Methods of manufacturing oxide thin film according to exampleembodiments include (A) applying an oxide precursor solution comprisingat least one of zinc (Zn), indium (In) and tin (Sn) on a substrate, (B)heat-treating the oxide precursor solution to form an oxide layer, and(C) repeating the steps (A) and (B) to form a plurality of the oxidelayers.

The thickness of the oxide layer may be about 10 Å to about 500 Å. Thethickness of the oxide layer may be about 10 Å to about 400 Å. Thethickness of the oxide layer may be a thickness of about 10 Å to about200 Å. The thickness of the oxide layer may be about 10 Å to about 100Å. The step (C) may be performed 2 to 20 times. The heat treatment ofthe oxide precursor solution may include primary heat treatment andsecondary heat treatment at higher temperature than the primary heattreatment. The secondary heat treatment may be conducted at about 300°C. or higher temperature.

The oxide precursor solution may include zinc (Zn) and indium (In). Theatomic ratio of zinc (Zn) and indium (In) in the oxide precursorsolution may be about 1:10 to about 10:1. The atomic ratio of zinc (Zn)and indium (In) in the oxide precursor solution may be about 1:5 toabout 5:1.

The oxide precursor solution may further include at least one metalselected from the group consisting of hafnium (Hf), magnesium (Mg),tantalum (Ta), cerium (Ce), lanthanum (La), gallium (Ga), zirconium(Zr), silicon (Si), germanium (Ge), vanadium (V), niobium (Nb), andyttrium (Y). The amount of the metal in the oxide precursor solution maybe less than or equal to about 50 at % based on the total atomic numberof the zinc and the indium. The steps (A) and (B) may be performed by asol-gel process. The interface region between the oxide layers may havea higher density than the internal region of each of the oxide layers.The oxide thin film may be amorphous. The oxide thin film may benanocrystalline. The oxide thin film may be amorphous andnanocrystalline. The oxide thin film may be a semiconductor.

An oxide thin film according to other example embodiments includes aplurality of oxide layers, each of the oxide layers including at leastone of zinc (Zn), indium (In) and tin (Sn). The thickness of the oxidelayer may be about 10 Å to about 500 Å. The thickness of the oxide layermay be about 10 Å to about 400 Å. The thickness of the oxide layer maybe about 10 Å to about 200 Å. The thickness of the oxide layer may beabout 10 Å to about 100 Å. The refractive index of the oxide thin filmincluding a plurality of oxide layers may be greater than the refractiveindex of a single oxide layer with the same thickness as the oxide thinfilm.

Each of the oxide layers may include zinc (Zn) and indium (In). Theatomic ratio of the zinc (Zn) and the indium (In) in the oxide layer maybe about 1:10 to about 10:1. The atomic ratio of the zinc (Zn) and theindium (In) in the oxide layer may be about 1:5 to about 5:1. The eachof the oxide layers may further include at least one metal selected fromthe group consisting of hafnium (Hf), magnesium (Mg), tantalum (Ta),cerium (Ce), lanthanum (La), gallium (Ga), zirconium (Zr), silicon (Si),germanium (Ge), vanadium (V), niobium (Nb), and yttrium (Y). Theinterface region between the oxide layers may have a higher density thanthe internal region of each of the oxide layers. The oxide thin film maybe amorphous. The oxide film may be nanocrystalline. The oxide film maybe amorphous and nanocrystalline. Electronic device according to stillother example embodiments may include the oxide thin film. The oxidethin film may be used as semiconductor.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will be more clearly understood from the followingbrief description taken in conjunction with the accompanying drawings.FIGS. 1-10 represent non-limiting, example embodiments as describedherein.

FIGS. 1-5 are cross-sectional diagrams illustrating methods ofmanufacturing oxide thin film according to example embodiments;

FIG. 6 is a transmission electron microscope (TEM) photograph of anoxide thin film including three oxide layers according to exampleembodiments;

FIG. 7 is a TEM photograph that is a magnification of “A” of FIG. 6;

FIG. 8 is a graph of refractive index (RI) as a function of thickness(Å) for IZO thin films according to two examples;

FIG. 9 is a graph of drain-to-source current (I_(DS) (A)) as a functionof gate voltage (V_(G) (V)) of thin film transistors manufacturedaccording to an example embodiment and a comparative example; and

FIG. 10 is a graph of refractive index (RI) as a function of thickness(Å) for oxide thin films manufactured according to example embodiments.

It should be noted that these figures are intended to illustrate thegeneral characteristics of methods, structure and/or materials utilizedin certain example embodiments and to supplement the written descriptionprovided below. These drawings are not, however, to scale and may notprecisely reflect the precise structural or performance characteristicsof any given embodiment, and should not be interpreted as defining orlimiting the range of values or properties encompassed by exampleembodiments. For example, the relative thicknesses and positioning ofmolecules, layers, regions and/or structural elements may be reduced orexaggerated for clarity. The use of similar or identical referencenumbers in the various drawings is intended to indicate the presence ofa similar or identical element or feature.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings, in which example embodiments are shown.Example embodiments may, however, be embodied in many different formsand should not be construed as being limited to the embodiments setforth herein; rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey theconcept of example embodiments to those of ordinary skill in the art. Inthe drawings, the thicknesses of layers and regions are exaggerated forclarity. Like reference numerals in the drawings denote like elements,and thus their description will be omitted.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Like numbers indicate like elementsthroughout. As used herein the term “and/or” includes any and allcombinations of one or more of the associated listed items. Other wordsused to describe the relationship between elements or layers should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” “on” versus “directlyon”).

It will be understood that, although the terms “first”, “second”, etc.may be used herein to describe various elements, components, regions,layers and/or sections, these elements, components, regions, layersand/or sections should not be limited by these terms. These terms areonly used to distinguish one element, component, region, layer orsection from another element, component, region, layer or section. Thus,a first element, component, region, layer or section discussed belowcould be termed a second element, component, region, layer or sectionwithout departing from the teachings of example embodiments.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises”, “comprising”, “includes” and/or “including,” if usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Example embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of exampleembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, example embodiments should not be construed aslimited to the particular shapes of regions illustrated herein but areto include deviations in shapes that result, for example, frommanufacturing. For example, an implanted region illustrated as arectangle may have rounded or curved features and/or a gradient ofimplant concentration at its edges rather than a binary change fromimplanted to non-implanted region. Likewise, a buried region formed byimplantation may result in some implantation in the region between theburied region and the surface through which the implantation takesplace. Thus, the regions illustrated in the figures are schematic innature and their shapes are not intended to illustrate the actual shapeof a region of a device and are not intended to limit the scope ofexample embodiments.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments belong. Itwill be further understood that terms, such as those defined incommonly-used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand will not be interpreted in an idealized or overly formal senseunless expressly so defined herein.

FIGS. 1-5 are cross-sectional diagrams illustrating methods ofmanufacturing oxide thin films according to example embodiments.Referring to FIG. 1, an oxide precursor solution including at least oneof zinc (Zn), indium (In) and tin (Sn) may be prepared. The oxideprecursor solution may be applied on a substrate 110 by, for example,spin coating, slit coating or Inkjet printing. The applied oxideprecursor may be dried to form an oxide precursor layer 120 a 1 by, forexample, a sol-gel process.

Referring to FIG. 2, the oxide precursor layer 120 a 1 may betransformed into an oxide layer 120 b 1. For example when the oxideprecursor layer 120 a 1 is heat-treated, the oxide precursor layer 120 a1 may be oxidized to form the oxide layer 120 b 1. According to exampleembodiments, one or more heat treatments may be performed. For example,the heat treatment may be performed twice, and may include the primaryheat treatment and the secondary heat treatment. The secondary heattreatment may be performed at higher temperature than the primary heattreatment. The secondary heat treatment may be performed at about 300°C. or higher temperature. For example, the primary heat treatment may beperformed at about 100° C. to about 300° C. and the secondary heattreatment may be performed at about 300° C. to about 1000° C.

The oxide layer 120 b 1 may be thin. For example, according to exampleembodiments the oxide layer 120 b 1 may be formed to the thickness ofabout 10 Å to about 500 Å. According to other example embodiments, thethickness of the oxide layer 120 b 1 may be about 10 Å to about 400 Å.According to still other example embodiments, the thickness of the oxidelayer 120 b 1 may be about 10 Å to about 200 Å. According to still otherexample embodiments, the thickness of the oxide layer 120 b 1 may beabout 10 Å to about 100 Å.

Referring to FIG. 3, an oxide precursor solution may be reapplied on theoxide layer 120 b 1 to form an oxide precursor layer 120 a 2. Forexample, the oxide precursor solution described with respect to FIGS. 1and 2 may be reapplied using a sol-gel process to form the oxideprecursor layer 120 a 2. Referring to FIG. 4, the oxide precursor layer120 a 2 may be transformed into an oxide layer 120 b 2. When the oxideprecursor layer 120 a 2 is heat-treated, the oxide precursor layer 120 a2 may be oxidized to form the oxide layer 120 b 2. The oxide layer 120 b2 may be thin. For example, according to example embodiments, the oxidelayer 120 b 2 may be formed to the thickness of about 10 Å to about 500Å. According to other example embodiments the thickness of the oxidelayer 120 b 2 may be formed to a thickness of about 10 Å to about 400 Å.According to still other example embodiments the oxide layer 120 b 2 maybe formed to a thickness of about 10 Å to about 200 Å. According tostill other example embodiments the oxide layer 120 b 2 may be formed toa thickness of about 10 Å to about 100 Å.

Referring to FIG. 5, the application of the oxide precursor solution andthe heat treatment of the oxide precursor layer may be repeatedlyperformed to form an oxide thin film 120 including a plurality of oxidelayers 120 b 1-120 bn, wherein n is a natural number (e.g., 1, 2, 3 . .. n).

For example, application of the oxide precursor solution and heattreatment of an oxide precursor layer may be performed 2 to 20 times.

Each oxide layer 120 b 1-120 bn may include an internal region with aplurality of pores and at least one interface region between the oxidelayers 120 b 1-120 bn having higher density than the internal region.The plurality of pores may be produced during the formation by sol-gelprocess. The density may be confirmed by, for example, the refractiveindex and a transmission electron microscope (TEM) photograph of theoxide thin film.

According to example embodiments, each oxide layer 120 b 1-120 bn may beformed sufficiently thin to decrease the internal region with pores andincrease the interface regions between the oxide layers with highdensity. Overall density of the oxide thin film 120 may be increased andpores produced during a sol-gel process may be reduced to preventdeterioration of mechanical-electrical characteristics of the oxide thinfilm 120 due to the pores. Reliability of electronic devices using anoxide thin film 120 as a semiconductor may be improved.

An oxide thin film 120 may be used for various electronic devices, forexample, a thin film transistor, an optical waveguide and/or a solarcell. An oxide thin film 120 in a thin film transistor may be used as,for example, an oxide semiconductor. An oxide thin film 120 in a solarcell may be used as, for example, an active layer. Example embodimentsare applicable to any electronic device including an oxide thin film(e.g., an oxide semiconductor).

An oxide precursor solution including at least one of zinc (Zn), indium(In) and tin (Sn) may disturb crystallization during heat treatment toform an amorphous and/or nanocrystalline oxide thin film. Herein, theterm “amorphous” means a material which does not exhibit any particularpattern in atomic order and the term “nanocrystalline” means a particleor grain having at least one dimension less than about 100 nm.

The oxide precursor solution may include, for example, at least one of azinc (Zn) containing precursor, an indium (In) containing precursor andtin (Sn) containing precursor. When the oxide precursor solutionincludes the zinc (Zn) containing precursor and the indium (In)containing precursor, the atomic ratio of the zinc to the indium in theoxide precursor solution may be about 1:10 to about 10:1, particularlyabout 1:5 to about 5:1. Within the above range, semiconductorcharacteristics may exist in an oxide layer.

The zinc containing precursor may be at least one of a zinc salt and ahydrate thereof, but is not limited thereto. The zinc containingprecursor may include, for example, zinc hydroxide, a zinc alkoxide, azinc citrate, a zinc acetate (e.g., zinc trifluoroacetate), a zinc(meth)acrylate, zinc nitrate, a zinc acetylacetonate (e.g., zinchexafluoroacetylacetonate, zinc chloride, zinc fluoride, and/or zincperchlorate), a zinc dialkyldithiocarbamate (e.g., zincdimethyldithiocarbamate and/or zinc diethyldithiocarbamate), a zincsulfonate (e.g., zinc trifluoromethanesulfonate), a zinc undecylenate, azinc borate (e.g., zinc tetrafluoroborate), and a hydrate thereof.

The indium containing precursor may be at least one of an indium saltand a hydrate thereof, but is not limited thereto. The indium containingprecursor may include indium hydroxide, an indium alkoxide (e.g., indiumisopropoxide), indium acetyl acetonate, indium acetate, an indium halide(e.g., indium chloride and/or indium fluoride), indium nitrate and ahydrate thereof.

The tin containing precursor may be at least one of a tin salt and ahydrate thereof, but is not limited thereto. The tin containingprecursor may include tin hydroxide, a tin alkoxide, tin acetylacetonate, tin acetate, a tin halide, tin nitrate and a hydrate thereof.

The oxide precursor solution may further include at least metal selectedfrom the group consisting of hafnium (Hf), magnesium (Mg), tantalum(Ta), cerium (Ce), lanthanum (La), gallium (Ga), zirconium (Zr), silicon(Si), germanium (Ge), vanadium (V), niobium (Nb), and yttrium (Y). Ametal containing precursor may be introduced, for example, as a halide(e.g., hafnium chloride (HfCl₄)), an acetate compound, a carbonylcompound, a carbonate compound, a nitride compound, and/or an alkoxidecompound.

The metal may be included in an amount of about 50 at % or less, basedon the total atomic number of at least one of zinc, indium and tin inthe oxide precursor solution. The metal may function for controlling athreshold voltage of the oxide thin film. At least one of the zinccontaining precursor, the indium containing precursor and the tincontaining precursor, and the metal containing precursor may be includedrespectively in the amount of about 0.01 to 30 wt %, based on the totalamount of the oxide precursor solution.

The oxide precursor solution may further include a solution stabilizer.The solution stabilizer may include, for example, at least one of anamine compound, an alcohol amine compound (e.g., monoethanolamine,diethanolamine, triethanolamine, N,N-methylethanolamine, aminoethylethanolamine, N-t-butylethanolamine, N,t-butyldiethanolamine, and/ordiethylene glycol amine), an alkyl ammonium hydroxide (e.g.,tetramethylammonium hydroxide, methylamine, ethylamine, and/ormonoisopropylamine), a ketone compound (e.g., acetylacetone, ammoniumhydroxide, potassium hydroxide, and/or sodium hydroxide), analkoxyalcohol (e.g., 2-(aminoethoxy)ethanol) and/or deionized water.

The solution stabilizer may be included in the oxide precursor solutionto increase solubility of the zinc containing precursor, the indiumcontaining precursor, the tin containing precursor and the metalcontaining precursor so as to form a uniform oxide layer. The solutionstabilizer may be included in an amount of about 0.01 to 30 wt % of thetotal amount of the oxide precursor solution.

According to example embodiments, a zinc containing precursor, an indiumcontaining precursor, a tin containing precursor, a metal containingprecursor and a solution stabilizer may be mixed in a solvent to beprepared an oxide precursor solution. Alternatively, the zinc containingprecursor, the indium containing precursor, the tin containing precursorand the metal containing precursor may be independently prepared andthen mixed.

The solution stabilizer may be added to the zinc containing precursor,the indium containing precursor, the tin containing precursor and themetal containing precursor, respectively. Alternatively, the solutionstabilizer may be added after mixing the zinc containing precursor, theindium containing precursor, the tin containing precursor and the metalcontaining precursor. For example, zinc acetate hydrate and indiumacetyl acetonate may be mixed in each solvent to independently prepare azinc acetate hydrate solution and an indium acetyl acetonate solution,the zinc acetate hydrate solution and the indium acetyl acetonatesolution may be mixed, and hafnium chloride and/or ahafnium-chloride-containing solution may be added thereto to prepare aprecursor solution. According to example embodiments, the zinccontaining precursor, the indium containing precursor, the tincontaining precursor, the metal containing precursor and the solutionstabilizer may be mixed in a solvent together to prepare an oxideprecursor solution.

The solvent may be any solvent that dissolves the zinc containingprecursor, the indium containing precursor, the tin containingprecursor, the metal containing precursor and the solution stabilizer.Non-limiting examples of the solvent may include at least one ofdeionized water, methanol, ethanol, propanol, isopropanol,2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol 2-butoxyethanol,methyl cellosolve, ethyl cellosolve, diethyleneglycol methylether,diethyleneglycolethylether, dipropyleneglycol methylether, toluene,xylene, hexane, heptane, octane, ethylacetate, butylacetate,diethyleneglycol dimethylether, diethyleneglycol dimethylethylether,methylmethoxy propionate, ethylethoxy propionate, ethyl lactate,propyleneglycol methylether acetate, propyleneglycol methylether,propyleneglycol propylether, methyl cellosolve acetate, ethyl cellosolveacetate, diethyleneglycol methyl acetate, diethyleneglycolethyl acetate,acetone, methylisobutylketone, cyclohexanone, dimethyl formamide (DMF),N,N-dimethyl acetamide (DMAc), N-methyl-2-pyrrolidone, γ-butyroctone,diethylether, ethyleneglycol dimethylether, diglyme, tetrahydrofuran,acetylacetone, and/or acetonitrile.

The following examples illustrate example embodiments in more detail.However, it is understood that the scope of example embodiments are notlimited to these examples.

Example 1 Preparation of Oxide Precursor Solution

Indium acetylacetonate (InAcac) was mixed in 2-methoxyethanol atconcentration of about 0.05M, and ethanolamine was added thereto in anamount of about 3 equivalents with regard to InAcac to prepare theindium acetylacetonate solution. Zinc acetate anhydrate was mixed in2-methoxyethanol at concentration of about 0.05M, and ethanolamine wasadded thereto in an amount of about 1 equivalent with regard to Zincacetate anhydrate to prepare the zinc acetate anhydride solution. Theindium acetylacetonate solution and the zinc acetate anhydride solutionwere mixed at the ratio of about 3:1 to prepare an oxide precursorsolution.

Formation of an Oxide Thin Film

The oxide precursor solution was spin-coated onto a silicon wafer. Thespin coating was performed at about 500 rpm for about 30 seconds. Aprimary heat treatment was performed at about 250° C. and a secondaryheat treatment was performed at about 450° C. for about 1 hour to forman IZO layer with thickness of about 120 Å. Processes of coating anoxide precursor solution on an IZO layer and heat treating the oxideprecursor solution were sequentially performed twice to form an oxidethin film including 3 IZO layers.

Example 2

Indium nitrate (In(NO₃)₃) and zinc acetate dihydrate were mixed at amole ratio of about 3:1 in 2-methoxyethanol at concentration of about0.1M, and ethanolamine and acetic acid were added to prepare an oxideprecursor solution.

Formation of an Oxide Thin Film

The oxide precursor solution was spin coated onto a silicon wafer. Thespin coating was performed at about 1500 rpm for about 30 seconds. Theprimary heat treatment was performed at about 300° C. and the secondaryheat treatment was performed at about 450° C. for about 1 hour to forman IZO layer with thickness of about 120 Å. Processes of coating anoxide precursor solution on an IZO layer and heat treating the oxideprecursor solution were sequentially performed twice to form an oxidethin film including 3 IZO layers.

Example 3

Indium nitrate hydrate, zinc acetate dihydride and gallium nitratehydrate were mixed at mole ratio of about 3:1:2 in 2-methoxyethanol atconcentration of about 0.1M, and ethanolamine and acetic acid were addedto prepare an oxide precursor solution including gallium.

Formation of an Oxide Thin Film

The oxide precursor solution was spin coated onto a silicon wafer. Thespin coating was conducted at about 3000 rpm for about 30 seconds. Aprimary heat treatment was performed at about 300° C. and a secondaryheat treatment was performed at about 550° C. for about 1 hour to form aGa-IZO layer. Processes of coating of an oxide precursor solution on aGa-IZO layer and heat treating the oxide precursor solution wereperformed 4 times to form an oxide thin film including 5 Ga-IZO layers.

Manufacture of Thin Film Transistor

Molybdenum tungsten (MoW) was deposited on a glass substrate to athickness of about 2000 Å, and was photolithographed to form a gateelectrode. Silicon nitride was deposited to a thickness of about 2000 Åby a chemical vapor deposition (CVD) method to form a gate insulatinglayer. An oxide precursor solution was spin coated onto the gateinsulating layer and a primary heat treatment was performed. The spincoating was performed at about 3000 rpm for about 30 seconds. Theprimary heat treatment was performed at about 300° C. for severalminutes. A secondary heat treatment was performed at about 550° C. forabout 1 hour in a furnace to form a Ga-IZO layer. Processes of coatingan oxide precursor solution on the Ga-IZO layer and heat treating theoxide precursor solution were conducted 4 times to form an oxide thinfilm including 5 Ga-IZO layers. Tantalum was deposited to a thickness ofabout 1000 Å, and a source electrode and a drain electrode were formedusing a shadow mask.

Example 4

Several silicon wafers were prepared. The oxide precursor solutionprepared as in [Example 1] was coated onto each silicon wafer. Thecoating amount of the oxide precursor solution on each silicon wafer wasvaried. A primary heat treatment was performed at about 250° C. and asecondary heat treatment was performed at about 450° C. for about 1 hourto form IZO layers with various thicknesses.

Comparative Example 1

Indium nitrate hydrate, zinc acetate dihydride and gallium nitratehydrate were mixed at a mole ratio of about 3:1:2 in 2-methoxyethanol atconcentration of about 0.5M, and ethanolamine and acetic acid were addedto prepare an oxide precursor solution including gallium.

Oxide Thin Film

The oxide precursor solution was spin coated onto a silicon wafer. Thespin coating was performed at about 3000 rpm for about 30 seconds. Aprimary heat treatment was performed at about 300° C. and a secondaryheat treatment was performed at about 550° C. for about 1 hour to form asingle oxide layer of Ga-IZO with the same thickness as 5 Ga-IZO layersaccording to [Example 3]

Manufacture of Thin Film Transistor

A thin film transistor was manufactured by substantially the same methodas described above with respect to [Example 3], except that the singleoxide layer of Ga-IZO with a thickness of about 430 Å was formed as asemiconductor layer by spin coating, instead of the 5 Ga-IZO layers.

Evaluation

Thin Film Formation

FIG. 6 is a transmission electron microscope (TEM) photograph of anoxide thin film including 3 sequentially deposited layers according to[Example 2]. FIG. 7 is a TEM photograph that is a magnification of “A”of FIG. 6. Referring to FIGS. 6 and 7, formation of an oxide thin filmaccording to [Example 2] was confirmed. An oxide thin film 120 including3 IZO layers was formed on the silicon wafer 110 according to the methoddescribed above with respect to [Example 2]. The interface regions 120 cbetween the IZO layers were dark compared to the internal regions 120 dof each IZO layer, which confirmed that the interface regions 120 cbetween the IZO layers is of higher density than the internal regions120 d of the IZO layer.

Refractive Index-1

FIG. 8 is a graph of refractive index (RI) as a function of thickness(Å) for IZO thin films according to two examples. The refractive indexwas measured for oxide thin films with 1, 2, and 3 layers, the layersformed according to [Example 1] and [Example 2]. Referring to FIG. 8,oxide thin films according to [Example 1] including 1, 2 or 3 IZO layerswith thickness of about 120 Å each were formed. The refractive indexgradually increased as the number of layers increased. Oxide thin filmsaccording to [Example 2] including 1, 2 and 3 IZO layers with athickness of about 120 Å each were formed. The refractive indexgradually increased as the number of layers increased.

According to FIG. 8, as a plurality of thin IZO layers are formed, aratio of the internal regions of the IZO layers to the total thicknessof the oxide thin film decreased while the ratio of interface regionsbetween the IZO layers to the total thickness of the oxide thin filmincreased, as compared to a single layer with the same thickness as aplurality of thin IZO layers, thereby increasing the total density ofthe oxide thin film.

Refractive Index-2

Refractive indices of oxide thin films manufactured according to[Example 3] and [Comparative Example 1] were compared in Table 1(below).

TABLE 1 [Example 3] [Comparative Example 1] Refractive index 1.81 1.76

As shown in Table 1, for oxide thin films with the same thickness, therefractive index of an oxide thin film including 5 thin layers accordingto [Example 3] was higher than the refractive index of a single oxidelayer according to [Comparative Example 1].

Thin Film Transistor Characteristic

FIG. 9 is a graph of drain-to-source current (IDS (A)) as a function ofgate voltage (VG (V)) of thin film transistors manufactured according to[Example 3] and [Comparative Example 1]. Table 2 (below) is a table ofmeasured charge mobilities for thin film transistors prepared accordingto [Example 3] and [Comparative Example 1].

TABLE 2 [Example 3] [Comparative Example 1] Charge mobility 1.32 0.85(cm²/Vs)

Referring to FIG. 9 and Table 2, for oxide layers with the samethickness used as semiconductor layers in transistors, charge mobilityof an oxide thin film including a plurality of oxide layers was greaterthan charge mobility of a single oxide layer with the same thickness asthe oxide thin film. An oxide thin film according to example embodimentsmay be of higher density and improved film quality as compared to asingle oxide layer.

Refractive Index-3

FIG. 10 is a graph of refractive index (RI) as a function of thickness(Å) for oxide thin film with various thicknesses prepared according to[Example 4]. Referring to FIG. 10, for the thickness of an oxide thinfilm of about 200 Å or less, the refractive index increased as thicknessdecreases.

While example embodiments have been particularly shown and described, itwill be understood by one of ordinary skill in the art that variationsin form and detail may be made therein without departing from the spiritand scope of the claims.

1. A method of manufacturing an oxide thin film, comprising: (A)applying an oxide precursor solution comprising at least one of zinc(Zn), indium (In) and tin (Sn) on a substrate, (B) heat-treating theoxide precursor solution to form an oxide layer, and (C) repeating thesteps (A) and (B) to form a plurality of the oxide layers.
 2. The methodof claim 1, wherein the thickness of the oxide layer is about 10 Å toabout 500 Å.
 3. The method of claim 1, wherein the thickness of theoxide layer is about 10 Å to about 400 Å.
 4. The method of claim 1,wherein the thickness of the oxide layer is about 10 Å to about 200 Å.5. The method of claim 1, wherein the thickness of the oxide layer isabout 10 Å to about 100 Å.
 6. The method of claim 1, wherein the step(C) is performed 2 to 20 times.
 7. The method of claim 1, wherein theheat-treating the oxide precursor solution comprises: a primary heattreatment, and a secondary heat treatment at higher temperature than theprimary heat treatment.
 8. The method of claim 7, wherein the secondaryheat treatment is conducted at about 300° C. or higher temperature. 9.The method of claim 1, wherein the oxide precursor solution compriseszinc (Zn) and indium (In).
 10. The method of claim 9, wherein an atomicratio of zinc (Zn) to indium (In) in the oxide precursor solution isabout 1:10 to about 10:1.
 11. The method of claim 9, wherein an atomicratio of zinc (Zn) to indium (In) in the oxide precursor solution isabout 1:5 to about 5:1.
 12. The method of claim 1, wherein the oxideprecursor solution further comprises at least one metal selected fromthe group consisting of hafnium (Hf), magnesium (Mg), tantalum (Ta),cerium (Ce), lanthanum (La), gallium (Ga), zirconium (Zr), silicon (Si),germanium (Ge), vanadium (V), niobium (Nb), and yttrium (Y).
 13. Themethod of claim 12, wherein an amount of the metal in the oxideprecursor solution is less than or equal to about 50 at % based on atotal atomic number of at least one of zinc, indium and tin.
 14. Themethod of claim 1, wherein the steps (A) and (B) are performed by asol-gel process.
 15. The method of claim 1, wherein the interface regionbetween the oxide layers has a higher density than the internal regionof each of the oxide layers.
 16. The method of claim 1, wherein theoxide thin film is amorphous.
 17. The method of claim 1, wherein theoxide thin film is nanocrystalline.
 18. The method of claim 1, whereinthe oxide thin film is amorphous and nanocrystalline.
 19. The method ofclaim 1, wherein the oxide thin film is a semiconductor.
 20. An oxidethin film, comprising: a plurality of oxide layers, each of the oxidelayers comprising at least one of zinc (Zn), indium (In) and tin (Sn).21. The oxide thin film of claim 20, wherein the thickness of each ofthe oxide layers is about 10 Å to about 500 Å.
 22. The oxide thin filmof claim 20, wherein the thickness of each of the oxide layers is about10 Å to about 400 Å.
 23. The oxide thin film of claim 20, wherein thethickness of each of the oxide layers is about 10 Å to about 200 Å. 24.The oxide thin film of claim 20, wherein the thickness of each of theoxide layers is about 10 Å to about 100 Å.
 25. The oxide thin film ofclaim 20, wherein the refractive index of the oxide thin film includinga plurality of oxide layers is greater than the refractive index of asingle oxide layer with the same thickness as the oxide thin film. 26.The method of claim 20, wherein each of the oxide layers comprises zinc(Zn) and indium (In).
 27. The oxide thin film of claim 26, wherein anatomic ratio of zinc (Zn) to indium (In) in the oxide layer is about1:10 to about 10:1.
 28. The oxide thin film of claim 26, wherein anatomic ratio of zinc (Zn) to indium (In) in the oxide layer is about 1:5to about 5:1.
 29. The oxide thin film of claim 20, wherein each of theoxide layers further comprises at least one metal selected from thegroup consisting of hafnium (Hf), magnesium (Mg), tantalum (Ta), cerium(Ce), lanthanum (La), gallium (Ga), zirconium (Zr), silicon (Si),germanium (Ge), vanadium (V), niobium (Nb), and yttrium (Y).
 30. Theoxide thin film of claim 20, wherein the interface region between theoxide layers has a higher density than the internal region of each ofthe oxide layers.
 31. The oxide thin film of claim 20, wherein the oxidethin film is amorphous.
 32. The oxide thin film of claim 20, wherein theoxide thin film is nanocrystalline.
 33. The oxide thin film of claim 20,wherein the oxide thin film is amorphous and nanocrystalline.
 34. Theoxide thin film of claim 20, wherein the oxide thin film is asemiconductor.
 35. The oxide thin film of claim 20, wherein the chargemobility of the oxide thin film including a plurality of oxide layers isgreater than the charge mobility of a single oxide layer with the samethickness as the oxide thin film.
 36. An electronic device comprisingthe oxide thin film of claim
 20. 37. The electronic device of claim 36,wherein the oxide thin film is a semiconductor.